Identification
A:
Proceed as directed in the following thin-layer chromatographic procedure.
Naphazoline hydrochloride standard solution
Dissolve a quantity of
USP Naphazoline Hydrochloride RSin water to obtain a solution containing about 1.5mg per mL.
Pheniramine maleate standard solution
Dissolve a quantity of
USP Pheniramine Maleate RSin water to obtain a solution containing about 6.0mg per mL.
Test solution
Dilute,if necessary,a volume of Ophthalmic Solution with water to obtain a solution containing about 0.25mg of naphazoline hydrochloride per mLand 3mg of pheniramine maleate per mL.
Procedure
Separately apply 5µLof
Naphazoline hydrochloride standard solution,10µLof
Pheniramine maleate standard solution,and 30µLof the
Test solutionto a 20-cm ×20-cm thin-layer chromatographic plate (see
Chromatography á621ñ)coated with a 0.25-mm layer of silica gel.Allow the spots to dry,then place the plate in a saturated chromatographic chamber,and develop in a solvent system consisting of methanol,water,and acetic acid (8:1:1)until the solvent front has moved to about 1.5cm from the top of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow to air-dry.Spray with ninhydrin TS,and place in an oven at 105

to visualize the spots.Both the naphazoline and pheniramine spots are purplish grey in color.The
RFvalues of the spots obtained from the
Test solutioncorrespond to those obtained from the
Naphazoline hydrochloride standard solution and the
Pheniramine maleate standard solution.
B:
The retention times of the major peaks in the chromatogram of the Assay preparationcorrespond to those of the Standard preparation,as obtained in the Assay.
Assay
Buffer solution
Dissolve 14.2g of anhydrous dibasic sodium phosphate and 20mLof triethylamine in 1900mLof water,adjust with phosphoric acid to a pHof 5.6±0.1,dilute with water to make 2000mLof solution,and mix.
Mobile phase
Prepared a filtered and degassed mixture of
Bufferand acetonitrile (80:20).Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Naphazoline hydrochloride stock standard solution
Dissolve an accurately weighed quantity of
USP Naphazoline Hydrochloride RSin
Mobile phaseto obtain a solution having a known concentration of about 0.75mg per mL.
Pheniramine maleate stock standard solution
Dissolve an accurately weighed quantity of
USP Pheniramine Maleate RSin
Mobile phaseto obtain a known concentration of about 3.00mg per mL.
Standard preparation
Transfer 1.0mLof Naphazoline hydrochloride stock standard solutionand 3.0mLof Pheniramine maleate stock standard solutionto a 25-mLvolumetric flask,dilute with Mobile phaseto volume,and mix to obtain a solution having known concentrations of naphazoline hydrochloride and pheniramine maleate of 0.03and 0.36mg per mL,respectively.
Assay preparation
Transfer an accurately measured volume of Ophthalmic Solution,equivalent to about 0.75mg of naphazoline hydrochloride and 9.0mg of pheniramine maleate,to a 25-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
Chromatographic system (see Chromatography á621ñ)
The liquid chromatograph is equipped with a 270-nm detector and a 4.6-mm ×15-cm column that contains packing L7.The flow rate is about 1.5mLper minute.Chromatograph the
Standard preparation,and record the peak responses as directed for
Procedure:the resolution,
R,between the naphazoline peak and the pheniramine peak is not less than 2;the column efficiency,determined from the naphazoline and pheniramine peaks,is not less than 750theoretical plates;the tailing factor is not greater than 2.5for pheniramine;and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure
Separately inject equal volumes (about 25µL)of the
Standard preparationand the
Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the peaks.Calculate the quantity,in mg,of naphazoline hydrochloride (C
14H
14N
2·HCl)in each mLof the Ophthalmic Solution taken by the formula:
25(C/V)(rU/rS),
in which
Cis the concentration in mg per mLof
USP Naphazoline Hydrochloride RSin the
Standard preparation;Vis the volume,in mL,of Ophthalmic solution taken;and
rUand
rSare the naphazoline peak responses obtained from the
Assay preparation and the
Standard preparation,respectively.Calculate the quantity,in mg,of pheniramine maleate (C
16H
20N
2·C
4H
4O
4)in each mLof the Ophthalmic Solution taken by the same formula,changing the terms to refer to pheniramine maleate.